OVERVOLTAGE PROTECTOR FOR SEMICONDUCTOR CIRCUIT DEVICE

摘要

PURPOSE:To provide a low limiting voltage against an overvoltage by a method wherein a semiconductor layer for transistor use is formed inside a semiconductor region and a collector layer and a base layer whose conductivity type is opposite to that of the collector layer are connected in series so that a reverse- direction voltage can be impressed. CONSTITUTION:A semiconductor layer for transistor use is formed inside a semiconductor region 13 which is separated electrically from a substrate 10. A collector layer 21 and a base layer 22 whose conductivity type is opposite to that of the collector layer at least in the semiconductor layer for transistor use are connected in series between a wiring part 50 to be protected against an overvoltage and an operating reference potential point of a semiconductor circuit device so that a reverse-direction voltage can be impressed on a semiconductor junction between the layers. While the reverse-direction voltage is impressed between the collector layer and the base layer, the overvoltage is limited by their breakdown strength or breakdown voltage. By this setup, a protective device can have a limiting voltage which is lower than a conventional limiting voltage and which is best fitted to a characteristic of a circuit element.